foo.diff

diff --git a/mezzanine/generic/fields.py b/mezzanine/generic/fields.py
index 8d8dd94..e95de37 100644
--- a/mezzanine/generic/fields.py
+++ b/mezzanine/generic/fields.py
@@ -134,6 +134,12 @@ class BaseGenericRelation(GenericRelation):
         """
         pass
 
+    def value_from_object(self, obj):
+        """
+        Returns the value of this field in the given model instance.
+        """
+        return getattr(obj, self.attname).all()
+
 
 class CommentsField(BaseGenericRelation):
     """